Research Of Shadow Rendering In The Visual System Of Marine Simulator

Visual systems are important ingredients of maritime simulators, which could present the vivid simulation of ships and their surrounding environments. Shadows could enhance the level of realism of the three-dimensional graphics, provide visual cues to decide spatial relationships of objects in the scene and help the navigating staff to gain the accurate information of positions for navigating the ships.This dissertation mainly studies the shadows rendering techniques in visual systems and tries to improve the rendering efficiency on the condition that these techniques could satisfy the rendering realism. The deep study of shadows rendering, especially of trestle, rescue helicopter and the wharf, has accomplished satisfied results. The main contributions of this dissertation are:This dissertation studies the shadow map algorithm and puts forward multilayer shadow map Algorithm based on the percentage-split, aiming at solving the shadow map edge aliasing. According to the distance of objects and view point, this algorithm uses percentage-split to split the shadow map, reduces the resource of buffer and improves the sampling rate of scenes nearing the view point, thus reducing the aliasing.As shadow volume algorithm's filling rate is high and could not be able to render the complicate scenes, an optimized shadow volume algorithm is proposed. First, this algorithm defines the shadows rendering area. Then, depending on whether the view point is in the shadow volume, this algorithm chooses Depth-pass or Depth-fail to accelerate the shadows rendering and improve the rendering efficiency. Automatic capping algorithm is adopted to assure the accurate generation of shadow volumes. V-buffer based soft shadow algorism is proposed to improve Shadow volume algorithm. The new algorithm shows the lighting of the shadow region on GPU and realizes the hardware-accelerated soft shadows rendering.Ray tracing shadow algorithm is proposed, aiming at dealing with the large amount of calculation and slow calculation speed. This algorithm tries to apply ray tracing algorithm of the collision of light and object and calculation methods of light fraction on GPU. To certain extent, it improves the ray tracing algorithm rendering speed.